If you think you may have found a bug in GNU Emacs, please
read the Bugs section of the Emacs manual for advice on
(1) how to tell when to report a bug, and
(2) how to write a useful bug report and what information
it needs to have.
There are three ways to read the Bugs section.
(1) In a printed copy of the Emacs manual.
You can order one from the Free Software Foundation;
see the file etc/ORDERS. But if you don't have a copy on
hand and you think you have found a bug, you shouldn't wait
to get a printed manual; you should read the section right away
as described below.
(2) With Info. Start Emacs, do C-h i to enter Info,
then m Emacs RET to get to the Emacs manual, then m Bugs RET
to get to the section on bugs. Or use standalone Info in
a like manner. (Standalone Info is part of the Texinfo distribution,
not part of the Emacs distribution.)
(3) By hand. Do
cat info/emacs* | more "+/^File: emacs, Node: Bugs,"
Please first check the file etc/PROBLEMS (e.g. with C-h C-e in Emacs) to
make sure it isn't a known issue.